In 2001, over 1.2 million new cases of human cancer will be diagnosed and over 0.5 million people will die from cancer (American Cancer Society estimate). Despite this, more people than ever are living with and surviving cancer. In 1997, for example, approximately 8.9 million living Americans had a history of cancer (National Cancer Institute estimate). People are more likely to survive cancer if the disease is diagnosed at an early stage of development, since treatment at that time is more likely to be successful. Early detection depends upon availability of high-quality methods. Such methods are also useful for determining patient prognosis, selecting therapy, monitoring response to therapy and selecting patients for additional therapy. Consequently, there is a need for cancer diagnostic methods that are specific, accurate, minimally invasive, technically simple and inexpensive.
Gastrointestinal cancers affect millions of patients per year. For example, over 15,000 new cases of esophageal cancer were diagnosed in 2010, and there were nearly as many deaths from this cancer alone. Similarly, about 21,000 new cases of stomach cancer were diagnosed in 2010, and over 10,000 deaths resulted from stomach cancer. The occurrence of colorectal cancer (i.e., cancer of the colon or rectum) is even higher. Approximately 40% of individuals with colorectal cancer die. In 2011, it is estimated that there will be over 141,000 new cases of colorectal cancer (101,700 cases of colon and 39,510 cases of rectal cancer) and about 50,000 deaths (all statistics: American Cancer Society). As with other cancers, these rates can be decreased by improved methods for diagnosis. Although methods for detecting each type of cancer exist, the methods are not ideal. Generally, a combination of endoscopy, isolation of cells (for example, via collection of cells/tissues from a fluid sample or from a tissue sample), and/or imaging technologies are used to identify cancerous cells and tumors. There are also a variety of tests conducted for each specific cancer, but these have limitations. For example, colon cancer may be detected with digital rectal exams (i.e., manual probing of rectum by a physician), which are relatively inexpensive, but are unpleasant and can be inaccurate. Fecal occult blood testing (i.e., detection of blood in stool) is nonspecific because blood in the stool has multiple causes. Colonoscopy and sigmoidoscopy (i.e., direct examination of the colon with a flexible viewing instrument) are both uncomfortable for the patient and expensive. Double-contrast barium enema (i.e., taking X-rays of barium-filled colon) is also an expensive procedure, usually performed by a radiologist. Upper endoscopy, an examination of the esophagus, stomach and duodenum, usually performed by a gastroenterologist, can detect neoplasias of these organs, but is also an uncomfortable and expensive procedure.
Because of the disadvantages of existing methods for detecting or treating cancers, new methods are needed for cancer diagnosis and therapy.